The present invention relates to a recording and reproducing apparatus, and particularly to a magneto-optical disc recording and reproducing apparatus.
Various recording formats have been proposed for magneto-optical discs. FIG. 9 shows a sector format of a 5.25-inch magneto-optical disc for recording user data at 512 bytes/sector, and FIG. 10 shows a sector format of a 5.25-inch magneto-optical disc for recording user data at 1024 bytes/sector. These sector formats differ only in the lengths of data field and buffer.
The sector formats shown in FIGS. 9 and 10 include an address field, a flag field, a data field, and a buffer.
The address field is a region having a record of a physical block address that is the physical address of the sector on the disc, and it is preformatted in the form of pits on the disc substrate. The flag field is a region in which flags indicative of the state of data in the sector are recorded. The data field is a region in which user data is recorded. The buffer is a marginal region provided so that the data field and the address field of the neighboring sector do not overlap in the event of a fluctuating disc rotation at recording.
The address field begins with a lead pattern called sector mark (SM), which is followed by three repetitive address information patterns each including a pattern of variable frequency oscillator (VFO) which provides the rotational phase of the revolving disc, an address mark (AM) which indicates the address data starting position and an identifier (ID) which contains a track number, sector number and cyclic redundancy check (CRC) code used for the detection of reproduction error, and ends with a postamble (PA). The three identifiers (ID.sub.1, ID.sub.2, ID.sub.3) in the address field contain the same record of identification signal (ID signal).
The flag field includes a flag (FLAG) which indicates that data has been recorded, an offset detection flag (ODF) which is a mark for the tracking offset detection based on the push-pull scheme, and a region of automatic laser power control (ALPC) used for the adjustment of laser power level.
The data field includes a region for the record of PLL data pattern used for the variable frequency oscillator (VFO), a region for the record of data sync signal (SYNC), and a data field for recording user data, control bytes used for recording data in a relief sector in the case of a defective sector, error correction code (ECC), cyclic redundancy check (CRC) code used for error detection, and special code pattern (RESYNC) used for synchronization.
Based on the conventional sector formats shown in FIGS. 9 and 10, in which the same ID signal is recorded repeatedly in three address fields for coping with defects on the disc, the operation of data write (recording) mode proceeds when the ID signal is read out correctly from at least two of three identifiers and the operation of data read (reproducing) mode proceeds when the ID signal is read out correctly from at least one identifier.
A problem of the above-mentioned conventional sector formats is that having three records of identifiers in each sector is too redundant.